The following is provided as background information only. Nothing in this section is intended to be, nor should it be construed as, prior art to the subject invention.
Rope ladders have many uses. For example, they can serve as emergency escape means from buildings, ships at sea and other elevated structures. They are also useful as boarding and disembarking means for ships. In particular, rope ladders are the default means for harbor pilots to board ships to take control of navigating the ships safely to dock. To ensure to the extent possible the safety of rope ladders for marine use, the U.S. Coast Guard has mandated specific requirements for the construction of marine-use rope ladders. Numerous patents have been issued directed to rope ladder construction that meet or exceed Coast Guard specifications.
One of the earliest patents relating to rope ladder construction that comports with Coast Guard regulations is U.S. Pat. No. 4,117,878, filed on 14 Aug. 1978 and issued on 11 Dec. 1979. Historically, rope ladder steps were made of wood. Wood steps, however, are susceptible to warping, breakage and general structural non-uniformity. The advent of superior strength polymers led to the development of molded steps made of tough, durable polymeric materials. Thus, U.S. Pat. No. 4,241,809, filed on 13 Aug. 1979 and issued on 30 Dec. 1980, was directed to rope ladders incorporating such molded elastomer steps. U.S. Pat. No. 4,554,996, filed on 12 Apr. 1985 and issued on 26 Nov. 1985 was directed to improvements to the polymeric steps and to the collars that secure the steps to the ropes of the ladder. U.S. Pat. No. 4,655,321, filed on 29 Aug. 1986 and issued on 7 Apr. 1987, was directed to an improved method for assembling rope ladders comprising molded polymeric steps. U.S. Pat. No. 4,683,981, filed on 4 Aug. 1986 and issued on 4 Aug. 1987, was directed to added beneficial features for molded elastomeric step rope ladders. More recently, U.S. Pat. No. 6,902,037 was filed on 2 Sep. 2003 and was issued on 7 Jun. 2005. The '037 patent is directed to a novel device for securing the rungs of a rope ladder to the ropes. Each of the foregoing patents was issued to Robert. M. Salvarezza, the inventor in the present application, and each of the above patents is incorporated by reference, including all drawings, as if fully set forth herein.
An important aspect, and a necessary one for marine-use rope ladders if they are to meet Coast Guard regulation, is the stability of rope ladders when deployed. Since the ropes are flexible, rope ladders tend to move, particularly to twist, in response to ship movement, wave action and wind, when deployed. To counter this movement, rope ladders may—and in the case of “pilot ladders” must by Coast Guard regulation—employ, in addition to normal rungs that extend only from one of the spaced-apart ropes or set of ropes to the other rope or ropes of the ladder, spreader steps that are substantially longer that the normal rungs and that extend a distance outward in each direction beyond the spaced apart ropes. The spreader steps contact the side of the ship and act as a stabilizing influence for the ladder, countering the tendency of the ladder to move, especially twist, in response to environmental conditions such as those mentioned above.
A problem with spreader steps is their longevity since they are especially prone to wear and tear during use. For instance, since they extend beyond the main bulk of a rope ladder when collapsed, they constitute a very convenient handhold for lifting and carrying the ladder. The weight of the rope ladder that is being borne by spreader steps so used can cause them to bend, even break, which by regulation requires their replacement and essentially renders them unusable, perhaps in critical situations, until such replacement is accomplished. What is needed is a spreader step that is capable of meeting not only Coast Guard regulation relating to resistance to bending and breakage under what the Coast Guard regards as normal use conditions but even to extraordinary use conditions such as that just mentioned above. This invention provides such a spreader step.